Method for holding a plate-like member

ABSTRACT

A semiconductor wafer receiving apparatus has a base, a table for supporting a wafer, a receiving member having at least three receiving pins which project from a supporting surface and are concealed under the supporting surface upon vertical movement of the table, and a driving unit for vertically moving the table. The wafer is transferred onto the receiving pins while the receiving pins project, and is held on the table while the receiving pins are concealed.

This is a division of application Ser. No. 07/281,224, filed on Dec. 8,1988 now U.S. Pat. No. 4,955,590.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a holding apparatus for holding aplate-like member such as a semiconductor wafer, and a method forholding the member.

2. Description of the Related Art

In the step of machining or inspecting a semiconductor in the process ofthe manufacture of a semiconductor, e.g., in the step of measuringelectrical characteristics of a wafer using a wafer prober, asemiconductor wafer conveyed by a conveyor belt or a robot arm from awafer carrier is placed on a convey arm after performed prealignment byway of positioning a flat orientation, and is transferred from theconvey arm to a chuck for supporting the semiconductor wafer whilechucking it.

In the wafer transfer step, a plurality of pins of projecting membersembedded in the chuck project from the surface of a holding table of thechuck, and the semiconductor wafer is transferred onto the projectingpins from the convey arm. The projecting members are moved downward andthe pins are concealed in the chuck, and then the wafer placed on thepins are chucked and fixed on the upper surface of the holding table. Inthis state, the chuck is intermittently moved for each wafer so that alarge number of probes supported to a probe card correspond to a largenumber of electrodes on each chip of the wafer.

Such a holding apparatus is disclosed in, for example, Japanese UtilityModel Publication No. 62--6691.

However, in the conventional holding apparatus, a semiconductor wafer asa plate-like member is transferred onto the plurality of pins projectingfrom the holding table, and thereafter, the pins are moved downward.Therefore, the speed of downward movement of the pins and that of thesemiconductor wafer which receives an air resistance differ from eachother, with the result that the wafer floats. In this case, thesemiconductor wafer performed prealignment is placed on an offsetposition on the holding table, and in the worst case, may be droppedfrom the holding table.

When the wafer is transferred from the convey arm to the pins of theprojecting members, noise is generated as the distal ends of the pins,which are being moved upward, collide against the wafer.

SUMMARY OF THE INVENTION

The present invention has been developed to solve the above problems,and has as its object to provide a plate-like member holding apparatuswhich can hold a plate-like member in a predetermined position, withoutmaking too much noise.

A plate-like member receiving apparatus according to the presentinvention comprises: a base unit; a table member having a supportingsurface on which a plate-like member is supported, and which isvertically movable with respect to the base unit; a receiving memberhaving at least three receiving pins which project from the supportingsurface and are concealed under the holding surface upon verticalmovement of the table member, movement of the receiving member relativeto the base unit being eliminated when the plate-like member issupported on the table member; and drive means for vertically moving thetable member, wherein the plate-like member is transferred onto thereceiving pins while the receiving pins project, and is supported on thesupporting surface of the table member while the pins are concealed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a receiving apparatus according to anembodiment of the present invention;

FIG. 2 is a sectional view showing a state wherein the apparatus shownin FIG. 1 receives a semiconductor wafer;

FIG. 3 is a sectional view showing a state wherein, when the apparatusshown in FIG. 1 is applied to a wafer probing machine, electrode pads ofa semiconductor wafer are brought into contact with probes;

FIG. 4 is a plan view showing a state wherein a semiconductor wafer istransferred from a convey arm onto pins; and

FIG. 5 is a side view of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will now be described withreference to the accompanying drawings. FIG. 1 is a sectional viewshowing a plate-like member received apparatus according to anembodiment of the present invention. The receiving apparatus comprisesbase unit 10, table unit 20 which is vertically movably arranged on baseunit 10, driving unit 30 for vertically moving table unit 20, andprojecting member 40 for receiving a semiconductor wafer whileprojecting from table unit 20.

Base unit 10 has base 11 having cylindrical projecting portion 114projecting downward, and outer cylinder 12 fixed to projecting portion11a by mounting members 13 and 14.

Table unit 20 has disk-like table 21 on which, semiconductor wafer 50 asa plate-like member, is held, and cylindrical member 22 which iscoaxially fixed to the lower surface of table 21 so that itslongitudinal direction coincides with the vertical direction.

Recess 26 capable of receiving main body of projecting member 40 (to bedescribed later) is formed in the central portion of the lower surfaceof table 21, and at least three (only two shown in FIG. 1 but three inthis embodiment) through holes 24 through which pins 42 (to be describedlater) of projecting member 40 are inserted are formed contiguous withrecess 26 to be perpendicular to the placing surface. Vacuum suctionhole 25 having an L-shaped section extends from the upper surface to theside surface of placing table 21. Hole 25 is coupled to vacuum pump 60through pipe 61. When pump 61 is operated, wafer 50 is chucked on theholding surface (upper surface) of table 21.

Cylindrical member 22 is arranged to be vertically movable along theinner wall of outer cylinder 12 of base unit 10. Cylindrical member 22has disk-like nut portion 23 having screw hole 23a at the center of theinner central portion. Bearing (also called ball bearing) 29 is arrangedbetween cylindrical member 22 and outer cylinder 12 so that cylindricalmember 22 can be easily vertically moved along outer cylinder 12.

Driving unit 30 comprises motor 31, coupling 32, and ball screw 33extending upward from coupling 32, and driven by motor 31. Ball screw 33is threadably engaged with screw hole 23a of nut portion 23, and whenball screw 33 is rotated by motor 31, placing unit 20 is verticallymoved. Semi-spherical distal end portion 34 is formed at the distal endof ball screw 33.

Projecting member 40 is vertically movably arranged on the inner upperend portion of cylindrical member 22. Projecting member 40 has main body41, and at least three (three this embodiment) pins 42 which areinserted in holes 24 when they project upward from main body 41, so asto support wafer 50. Collar portion 41a is formed along the outerperiphery of main body 41, and recess portion 41b is formed in thecentral portion of the lower surface of main body 41. When wafer 50 isreceived and placed on table 21, distal end portion 34 of ball screw 33of driving unit 30 abuts against recess portion 41b. Main body 41 issubstantially accommodated in recess 26 when table 21 is moved downwardand pins 42 project from the upper surface of table 21 upon transfer ofwafer 50. More specifically, upon transfer of wafer 50, movement ofprojecting member 40 is inhibited by distal end portion 34 of ball screw33, and only table 21 is moved. Note that the distal end portion of eachpin 42 is slightly tapered and rounded.

Mounting plate 45 is fixed to a portion, corresponding to recess 26, ofthe lower surface of table 21 by, e.g., screws. Three guide shafts 46(only two of them shown in FIG. 1) extending downward are attached tomounting plate 45. Holes 44 for receiving guide shafts 46 throughbearings 48 are formed in the main body of projecting member 40. Theprojecting member 40 can be smoothly moved without being displaced bythese guide shafts 46 and bearings 48. Spring 47 fixed to mounting plate45 and corresponding bearing 48 is arranged around each guide shaft 46.Projecting member 40 is biased downward by springs 47. E ring 49 servingas a stopper is provided near the lower end of each shaft 46.

Since guide shafts 46 and bearings 48 are arranged in this manner, arotational moment from ball screw 33 can be absorbed. Since pins 42 canbe prevented from being rubbed against portions of holes 24 of table 21,generation of dust can be prevented.

Note that cylindrical member 22 can be rotated along the inner wall ofouter cylinder 12 by a driver (not shown), thus allowing alignment ofthe semiconductor wafer on placing table 21.

The operation of the apparatus with the above arrangement will bedescribed below.

As shown in FIGS. 4 and 5, the holding apparatus of this embodiment isplaced immediately below plate-like convey arm 80 which conveys wafer 50to chuck it at suction hole 81 by a vacuum pump (not shown). Arm 80 hasnotch 82 for escaping from pins 42 when pins 42 project. Motor 31 isdriven to move table unit 20 downward. In this case, since distal endportion 34 of ball screw 33 abuts against recess portion 41b ofprojecting member 40, projecting member 40 is left in position, and onlytable unit 20 is moved downward. As a result, as shown in FIG. 2, pins42 of projecting member 40 project from the upper surface of placingtable 21. In this state, a plane is defined by three pins 42,semiconductor wafer 50 is transferred from convey arm 80 onto pins 42,and wafer 50 is then supported on pins 42, as shown in FIG. 5. Theprojecting height of each pin 42 is large enough to allow insertion andescaping of arm 80 upon transfer of wafer 50. During transfer of wafer50, arm 80 loading wafer 50 is located immediately above table 21, andafter transfer, arm 80 is escaped in a direction of arrow 90 in FIG. 4.

Motor 31 is then driven to move holding unit 20 upward. In this case,projecting member 40 is kept supported on ball screw 33, and only tableunit 20 is moved upward. Therefore, pins 42 of projecting member 40 areconcealed in holes 24 of table 21, and hence, wafer 50 is placed on theupper surface of table 21. Then, vacuum pump 60 is operated, so thatwafer 50 is chucked on the upper surface of table 21.

After predetermined inspection or machining is performed whilesemiconductor wafer 50 is chucked on table 21, the semiconductor waferis conveyed from the placing apparatus in procedures opposite to thesemiconductor wafer transfer procedures as described above.

The holding apparatus can be applied to a wafer probing machine. In thisprobing machine, a distance of upward movement of table unit 20 must bedetermined so that wafer 50 can be moved to a probing position. Thewafer probing machine has test head 70 to which wirings from a tester(not shown) are integrated. Test head 70 is located above theabove-mentioned placing apparatus. Performance board 71 is connected tothe lower surface of test head 70, and probe card 72, on the lowersurface of which a large number of probes 73 are formed, is connected toboard 71.

In the probing machine, semiconductor wafer 50 is chucked on table 21,as described above, and the holding apparatus is moved by an alignmentapparatus (not shown) to a position where a large number of electrodepads formed on each chip of wafer 50 correspond to probes 73. Motor 31is then driven to further move holding unit 20 upward, thereby bringingprobes 73 into contact with electrode pads of each chip of wafer 50 toperform measurement. In this case, projecting member 40 is separatedfrom ball screw 33.

As described above, according to the holding apparatus of thisembodiment, the projecting member having the pins for receiving a waferis not moved, and the table is moved to place a wafer thereon.Therefore, the wafer can be prevented from floating upon downwardmovement of the pins unlike in the conventional apparatus. Thus, thewafer can be stably held at a predetermined position. Therefore, theplacing operation of the wafer can be very efficiently performed. Sincethe pins are not moved, the distal ends of the pins do not collideagainst the wafer upon their upward movement, thus generating very smallnoise.

Since the ball screw is not directly coupled to the table, a stroke ofupward movement of the table can be increased. In addition, since theball screw is not directly coupled to the table, a vibration of thetable due to vibration of the motor can be eliminated, and displacementof the wafer on the table can be prevented.

In the above embodiment, the case has been described wherein the waferis held. The present invention is not limited to the wafer. For example,the present invention can be applied to a low-profile member such as anLCDE substrate. The case has been exemplified wherein the holdingapparatus is applied to the probing machine. However, the presentinvention is not limited to this but can be applied to various otherapparatuses which receive and hold a plate-like member.

The present invention is not limited to a wafer probing machine, but maybe applied to any other apparatuses which perform sheet-feed processing,such as an etching apparatus, a CVD apparatus, an ashing apparatus, andthe like.

In the above embodiment, a wafer is transferred onto three pins. Thenumber of pins can be three or more as long as a plate can be supportedthereon. In the above embodiment, a wafer is simply held on the pins. Asuction hole may be formed in the distal end of each pin to chuck awafer.

What is claimed is:
 1. A receiving method for receiving a plate-like member in a receiving apparatus having a vertically movable table member and at least three pins which project and retract upon vertical movement of said table member, comprising the steps of:moving said table member downward to cause said pins to project from said table member; placing said plate-like member on said pins; and moving said table member upward to conceal said pins under said table member, thereby receiving said plate-like member on said table member.
 2. The method according to claim 1, wherein said plate-like member is conveyed immediately above said pins projected from said table member by a convey member supporting said plate-like member thereon, and then said convey member is moved sideways, thereby said plate-like member is placed on said pins. 